Electric heater.



No. 796,684. PATEN'I'ED AUG. 8, 1905.

E. THOMSON. ELECTRIC HEATER.

APPLIOATION FILED JAN.13.1905.

UNITED STATES PATENT OFFIE.

ELIHU THOMSON, OE SwAMPsCOTT, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OE NEw YORK.

ELECTRIC HEATER.

Specification of Letters Patent.

Patented Aug. 8, 1905.

Application filed January 13, 1905. Serial N0. 240,856.

To all whom, tm/ty concern.

Be it known that I, ELIHU THOMSON, a citizen of the United States, residing at Swampscott, county of Essex, State of Massachusetts, have invented certain new and useful Improvements in Electric Heaters, of which the following is a specification.

This invention relates to electric heaters, and has for its object the provision of a device of this character which will be thoroughly economical and efcient, but which has a large heat-radiating surface in proportion to the power supplied.

More specifically, my invention pertains to electric heaters for cooking. The chief obstacles to the general introduction of electric heaters for cooking are, first, the necessity of sudden rushes of energy, demanding heavier mains and larger capacity of transformer apparatus to obtain heat at the proper rate; second, the necessity for a variety of utensils, all of which are electric and which are not interchangeable from one heater to another; third, apparatusof this construction would be diiiicult to keep clean. Grease would be spilled over the connections and deterioration become rapid. It is well known that a cooking utensil should have no opening or place where foreign matter could lodge either externally or internally, but should have smooth Outlines without angular projections,

and should be inexpensive to replace 1n case of damage or injury. An ideal cooking-range is therefore one that is permanently put in place, preferably without iiexible connections-one which uses steady and moderate current or energy delivery, but accumulates within itself the heat energy resulting therefrom. This means a thoroughly well jacketed affair to prevent escape of heat and one in which the resistance material can be easily looked after, inspected, and renewed.

In carrying out my invention I provide a stove which is heavily jacketed externally, provided with a lid of the same character. The construction of this stove is such that it becomes a heat-accumulator, so that the whole interior may become red-hot for a considerable time by a moderate expenditure of energy. Within this jacket I provide a mass of refractory material, preferably in lumps of substantially equal sizes, and I embed within this refractory mass a granular resistance material. The ladvantages of this construction will be made to appear in the course of the specification, in which I set forth a particular embodiment thereof, and the novelty of which I shall bring out in the claims appended to and forming a part of this specification.

Referring' to the drawings, Figure 1 is a vertical Section of a heater embodying my invention. Fig. 2 is a modified form thereof, and Fig. 3 is a diagrammatic view showing the circuits and the means for breaking the same.

Referring to Fig. 1, 1 is a metallic shell or casing, preferably of metal, as cast or sheet iron, or both, and provided with legs 2. This casing surrounds a jacketing material composed ofl a layer of some good heat-insulating substance, as asbestos, fire-clay, or mineralwool of any desired thickness. vThe lid 3 is constructed in a similar manner and secured to the lower portion in any desired manner, as by bolting. A removable plug L is likewise made to fit into the lid 3 and is constructed of the jacketing material, surrounded by metal, as shown. This casing is filled with lumps or a loose or broken mass of some refractory material 5, as quartz or a {ire-clay composition. Within this mass of refractory material I embed a granular resistance material 6, which will become heated upon the passage therethrough of electric current. Although I do not limit myself to the particular material to be used as a resistance, I have found that the element silicon possesses the characteristics which adapt it for use as a desirable resistance material. It has a high specific resistance, a high fusing-point, and a suitable temperature coeliicient, and, furthermore, it is not oxidized at high temperature. The terminals 7 and 8 pass through insulatingsleeves 9 and l0 in the casing and into contact with the resistance material- I make these terminals adjustable, so that I may increase or decrease the active length of the silicon bed.

In Fig. 2 the construction is very similar, with the exception that a water-tank 28 partially surrounds the jacket, which will Operate to save any heat which may leak through the jacketing and which will furnish warm water with a very small expenditure of energy. A plug similar to that used in Fig. l

. negative.

can likewise be used in this 'form of casing. In this form the jacket is preferably made thinner, so that some heat may find its way th roug'h to the water-tank. 1t has been found that when uncombined silicon, especially in the granular form, passes a red heat, `its temperature coefficient changes from positive to While it would seldom be advisable to heat the resistance above a. red heat. this might sometimes happen, and l therefore provide a means whereby the current is cut off when it reaches a certain predetermined point. Fig. 3 shows this arrangement. In this ligure the leads 11 12 supply energy to the heater 13 through the wires 14 and 15. A double-[wle switch 16 is provided in this circuit, which is automatically opened and closed in the following manner: `An overload-magnet 17 in theheating-circuitoperates upon a springpressed armature 13, which forms a part of the circuit of the battery 19 and by means of either contact S2() or 21 energizes either solenoid 22 or 23, which operates to open or close the switch.A as shown. Then the current reaches a predetermined point` the magnet 17 will draw the armature 13 so as to make contact at 21, and thereby energize solenoid 22, which will attract the core 24 and throw the switch into the position shown in dotted lines. This will prevent the resistance from becoming' too hot, and when the current again returns to its normal condition the spring 25 will draw the arn'lature 13 so as to make contact at 2l), which will energ'ize solenoid 23, which in turn will operate upon core 26 to close the switch. lt will thus be seen that I have provided a stove which can be turned on in the morning and run the greater part of the day without involving great cost and will be ready at any time for the work of cooking'. By ren'ioving the top or lid 3 an oven may be placed above the stove to enable it to be used for baking'. yl'y removing the plug in the lid a tea-kettle Q7 or other vessel may be inserted for boiling' or .frying or the lid may be removed and a gridiron placed over the red-hot mass within for purposes of broiling.

Many other simple modilications will suggest themselves as needs require.

That I. claim as new, and desire to secure by Letters Patent of the United States1 is- 1. An electric heater comprising a mass of refractory material and a mass of silicon embedded therein.

2. An electric heater comprising' a loose f tric resistance, and a lumpy mass of quartz in heat-conductive relation thereto.

3. An electric stove comprising a lumpy mass of refractory material, an electrical resistance Yfor heating the same` and a heat-insulating' jacket surrounding said mass.

9. An electric stove comprising a mass of refractory material, means within said mass for transfm'ming electric energy into heat, and a jacket surroundingsaid mass to prevent escape of heat.

10. An electric stove comprising a casing. a mass of material composed of lumps of refractory substance contained therein, a mass of granular resistance einl )e lded in said material, and electric terminals extending into contact with said resistance.

11. An electric stove comprising a jacketed casing containinfgil lumps of refractory material, an opening` through the upper side of the same, a mass of granular silicon embedded in said material, circuit-terminals in contact with said silicon, and n'ieans for opening' the circuit when the current reaches a predetermined point.

12. An electric stove comprising a jacketed casing containing lumps of refractory material?, an opening through the upper side of the same, a water-tank partially surrol'lndingsaid casing, a mass of granular silicon embedded in said material, an electric circuit having terminals in contact with said silicon, and means `for opening' said circuit when the current reaches a predetermined point.

In witness whereof I have hereunto set my hand this 11th day of January, 1905.

ELI IrlU TH O M SO N.

fitnessesz JOHN A. McManus, J r., DUGALD MGK. Molix'mor. 

